B2.1.5

• Water can move in and out of most cells freely.
• Osmosis is the net movement of solvent molecules from a region of high concentration to low concentration.
• Osmosis can happen in all cells because the water molecules are small enough to pass through the phospholipid bilayer.
• Some cells have water channels called aquaporins which increase the membrane permeability to water. f.e. kidney cells, root hair cells
• Aquaporins are very narrow to only allow water through. There are positive charges at a point in the channel to prevent protons (H+) from passing through.